Laura Erickson's For the Birds

Dog Days

(Recording of a Great Blue Heron)

The dog days of summer are here. My own personal dog’s exhaustion and discomfort are an excellent case study in how sweltering summer days came to be known as dog days. Dogs can’t sweat except on their footpads, which is hardly an effective cooling mechanism for a creature in a heavy fur coat. Labored panting, which makes me uncomfortable just watching, is a good symbol of the sheer unpleasantness of heat. But in the overall scheme of the universe, dogs are at least as stupid as they are good-natured, and so often in the blazing sun of midday, Bunter the Wonderdog can be found chasing sticks and bounding around in jolly games with my children. This of course means that when she finally lays down in exhaustion, her panting resounds throughout the house.

Hot weather affects birds much the same as dogs, except that bird’s can’t even sweat on their feet. Excessive heat can be much more lethal than excessive cold for birds, which don’t wear a canine fur coat–they’re encased in a thick down jacket year round. As with any mammal, birds need plenty of drinking water in hot weather. Bird baths are excellent, but it can be quite hard to keep the water clean, especially after grackle families discover them. Once a couple of birds have taken a bath, the water is usually too dirty for other birds to drink. And the problem is compounded by the many birds that for some mysterious reason dispose of egg shells and their nestling’s fecal sacs over water. Just last week I discovered robin egg shells in my bird bath–sure enough, my pair of robins is starting a new batch of babies–their third brood this summer.

In wild areas where there are no bird baths, puddles, streams, and the edges of lakes draw adult birds from literally miles around. Unfortunately, this isn’t much help to a nestling stuck at home. If a nest is exposed to the sun for part of the day, the babies can suffer heat exhaustion, and many cavity nesters literally roast to death, especially in metal bird houses. Ducklings, goslings, and loonlings can at least sit in the water to cool down, but large waterbirds, like Great Blue Herons, don’t get a whole lot of relief even outside of the nest. Standing in the water doesn’t help much because their legs and toes have too little blood circulation to carry the cooling to the rest of the body. But herons and some other species of water birds have at least perfected panting–they flutter their throat pouches, maximizing circulation as well as evaporation in the head area, which cools them more efficiently than panting in dogs. The noted ornithologist Arthur Cleveland Bent wrote about cormorant nestlings: “The heat of the sun on their black, naked bodies often brings fatal results, if they are left too long without the brooding care of their parents. Even when older and covered with black down, they seem to suffer greatly from the heat, panting with wide open mouths, the gular sacks vibrating rapidly as if in distress; perhaps this action may be caused by fear [from being observed] rather than by suffering, but it strongly suggests the panting of a dog on a hot day.”

Yep, the dog days of summer are certainly for the birds.

(Recording of a Great Blue Heron)

This is Laura Erickson, and this program has been “For the Birds.”